Benzyl alcohol
[CAS 100-51-6]

Identification

• Classification: API >> Anesthetic agents >> Local anesthetics
• Name: Benzyl alcohol
• Synonyms: alpha-Hydroxytoluene; alpha-Toluenol; Benzenecarbinol; Benzenemethanol; Phenylcarbinol; Phenylmethanol; Phenylmethyl alcohol
• Molecular Formula: C₇H₈O
• Molecular Weight: 108.13
• CAS Registry Number: 100-51-6
• EC Number: 202-859-9
• FEMA: 2137
• SMILES: C1=CC=C(C=C1)CO

Properties

• Density: 1.044
• Melting point: -15 °C
• Boiling point: 205 °C
• Refractive index: 1.538-1.541
• Flash point: 93 °C
• Water solubility: 4.29 g/100 mL (20 °C)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H332-H302
• Safety Statements: P261-P264-P264+P265-P270-P271-P280-P301+P317-P304+P340-P305+P351+P338-P317-P330-P337+P317-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H332
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H312
Serious eye damage	Eye Dam.	1	H318
Skin irritation	Skin Irrit.	2	H315
Skin sensitization	Skin Sens.	1	H317
Skin sensitization	Skin Sens.	1B	H317
Eye irritation	Eye Irrit.	2A	H319
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Acute toxicity	Acute Tox.	3	H331
Skin corrosion	Skin Corr.	1C	H314
Acute hazardous to the aquatic environment	Aquatic Acute	2	H401

Discovery and Applications

Benzyl alcohol is an aromatic compound with the chemical formula C₆H₅CH₂OH. Structurally, it consists of a benzene ring bonded to a hydroxymethyl group (-CH₂OH). This compound occurs naturally in essential oils from plants like jasmine and ylang-ylang and has been known to chemists since the 19th century. With its discovery and subsequent isolation, benzyl alcohol became widely recognized for its versatility, particularly in its role as a solvent, preservative, and intermediate in organic synthesis.

The most common method of synthesizing benzyl alcohol is the hydrolysis of benzyl chloride, which involves substituting the chlorine atom in benzyl chloride with a hydroxyl group. Another synthesis route is the reduction of benzaldehyde, converting the aldehyde group into a hydroxymethyl group. These processes have been refined to ensure that benzyl alcohol is readily available for use across various industries.

One of the most significant applications of benzyl alcohol is as a solvent. Due to its moderate polarity, it can dissolve a wide range of substances, making it particularly useful in the production of paints, coatings, resins, and inks. In epoxy resin systems, for example, it serves as a solvent that ensures the even dispersion of pigments and other ingredients, resulting in higher-quality coatings and finishes. Benzyl alcohol is also valued in the fragrance industry for dissolving aromatic compounds without altering their scent.

In the pharmaceutical industry, benzyl alcohol is extensively used as a preservative. Its antimicrobial properties, combined with its low toxicity, make it an ideal additive in injectable drugs, topical ointments, and skincare products. It effectively prevents bacterial and fungal contamination, ensuring that pharmaceutical products remain safe for use. In cosmetics, benzyl alcohol serves as a preservative and solvent in lotions, creams, and other personal care products, offering protection against microbial growth while contributing to product stability.

Benzyl alcohol also plays a role in dermatology as a treatment for head lice. It is used in lice treatment formulations approved for topical use, working by suffocating the lice rather than acting as a neurotoxin. This makes it an effective and safer alternative to traditional insecticidal treatments, particularly for children and individuals sensitive to harsher chemicals.

In organic chemistry, benzyl alcohol is a valuable starting material in the synthesis of numerous compounds. It is used to produce esters, ethers, and other derivatives in the manufacture of plastics, fragrances, and flavoring agents. Benzyl alcohol can be oxidized to benzaldehyde, a key intermediate in organic synthesis, especially for perfumes and food additives. It is also employed in the creation of benzyl esters, which find application as flavoring agents and solvents.

Art conservation is another field where benzyl alcohol is utilized. Its solvent properties make it effective for cleaning and restoring delicate surfaces, such as oil paintings, without damaging the underlying materials. This application demonstrates benzyl alcohol’s role beyond industrial and pharmaceutical uses, as it contributes to the preservation of cultural heritage.

Despite its many benefits, benzyl alcohol’s safety must be considered. In high concentrations, it can cause skin irritation or allergic reactions, although it is generally regarded as safe in regulated amounts for pharmaceuticals and cosmetics. In industrial settings, proper handling guidelines are essential to prevent potential health risks.

Overall, benzyl alcohol is a highly versatile compound with a wide range of applications in industries like pharmaceuticals, cosmetics, and organic synthesis. Its properties as a solvent, preservative, and chemical intermediate ensure its continued relevance in various sectors, from healthcare to the fine chemical industry.

References

2005. Characterization of Sphingomonas aldehyde dehydrogenase catalyzing the conversion of various aromatic aldehydes to their carboxylic acids. Applied Microbiology and Biotechnology, 68(4).
DOI: 10.1007/s00253-005-1962-x

2010. Optimization of immobilization for selective oxidation of benzyl alcohol by Gluconobacter oxydans using response surface methodology. Bioresource Technology, 101(23).
DOI: 10.1016/j.biortech.2010.07.019

2012. Unusual NADPH conformation in the crystal structure of a cinnamyl alcohol dehydrogenase from Helicobacter pylori in complex with NADP(H) and substrate docking analysis. FEBS Letters, 586(3).
DOI: 10.1016/j.febslet.2012.01.020